To search multiple words as a phrase enclose them in quotes.Example : "world health organization"
Without the quotes all words are searched as if joined by the and operator (all words must be present but can be anywhere).

Boolean Operators

Use and or or to specify multiple words in any field, any order. Combine these with not to specify exclusions and use parentheses to group expressions.Example : stocks and bonds Example : (alaska or canada) and (adventure and not vacation)

Wildcards

Truncate the end of a word with an asterisk (*) and use a question mark (?) to replace a single character anywhere in a word.Example : environment* polic*Example : wom?n

Proximity Operators

To specify words close to each other in any order, enclose them in quotes and add a tilde (~) followed by the maximum number of other words between them.Example : "fractal spectra"~5

Result Set Grouping

Results for simple searches are grouped by relevance to bring the most likely titles to the top of the list. Each group represents a similar level of relevance and results are sorted within the group by date or title. Complex searches return ungrouped results; to force ungrouped results use a set of quotes around a word.